Tiny Rocket Stove

arnon raab

Posts: 9

posted 1 year ago

Hello. I tried to build a small rocket stove. Feeder and tunner are 15mm on 20mm and the raiser diameter is 23mm. Can not start it... fire always stay in the feeder. Can anybody please help with advise of what am i doing wrong? Thank you. Arnon

By the look of it, the thing is made of clay. The ratio between the cross section area and the mass which surrounds it is huge. All the produced heat will be sucked up by the mass. It's also not possible to build e real fire in there, only toothpicks would be small enough. Besides that, instead of clay you should build it out of something that is insulating. And insulation, like fire, can't be scaled down limitless.

So it need to be a real fire surrounded by real insulation. I've built some 10x10 cm systems a couple of years ago and those were quite hard to get right already.

regards, Peter

arnon raab

Posts: 9

posted 1 year ago

Peter van den Berg wrote:By the look of it, the thing is made of clay. The ratio between the cross section area and the mass which surrounds it is huge.

Thank you. I m slight novis in this and can not completly understand why the RS can not be scalled down. It is made of craft white clay, burned once to 900c. I designed the feeder so 3 standing chopsticks take about 50% of the opening area. Why the big clay chunk is not acting like insulation, at least in the initial stage? If i would use cob instead, would it act differently? What would be good insulation here. Thank you

arnon raab wrote:Thank you. I m slight novis in this and can not completly understand why the RS can not be scalled down. It is made of craft white clay, burned once to 900c. I designed the feeder so 3 standing chopsticks take about 50% of the opening area. Why the big clay chunk is not acting like insulation, at least in the initial stage? If i would use cob instead, would it act differently? What would be good insulation here. Thank you

Those three chopsticks aren't going to make real fire, isn't it? So there need to be more burning surface in order to produce real high temperatures, in the range of 1000 C to be precise. The clay isn't full of small air pockets which would provide insulation, baked clay isn't airy but dense instead. With a larger fire, dense feed, tunnel and riser you'd need insulation like superwool or something like expanded vermiculite or perlite around it. Not just a centimeter, but 5 cm as a bare minimum whatever size the system is, isn't important. So please, place that small model somewhere on top of a cupboard and build another, bigger one. There isn't a chance in the world you could make this work.

And, more important, go to this webpage and order the book "rocket mass heaters", pdf version. Cost is $18 which is money very well spent. All the basic information you obviously need is in there.

regards, Peter

arnon raab

Posts: 9

posted 1 year ago

Peter van den Berg wrote:

arnon raab wrote:Thank you. I m slight novis in this and can not completly understand why the RS can not be scalled down. It is made of craft white clay, burned once to 900c. I designed the feeder so 3 standing chopsticks take about 50% of the opening area. Why the big clay chunk is not acting like insulation, at least in the initial stage? If i would use cob instead, would it act differently? What would be good insulation here. Thank you

Those three chopsticks aren't going to make real fire, isn't it? So there need to be more burning surface in order to produce real high temperatures, in the range of 1000 C to be precise. The clay isn't full of small air pockets which would provide insulation, baked clay isn't airy but dense instead. With a larger fire, dense feed, tunnel and riser you'd need insulation like superwool or something like expanded vermiculite or perlite around it. Not just a centimeter, but 5 cm as a bare minimum whatever size the system is, isn't important. So please, place that small model somewhere on top of a cupboard and build another, bigger one. There isn't a chance in the world you could make this work.

And, more important, go to this webpage and order the book "Rocket Mass Heaters", pdf version. Cost is $18 which is money very well spent. All the basic information you obviously need is in there.

Thank you very much Peter. I guess i ll have to accept that it can not scalled down...